JP5621318B2 - Semiconductor laser module and fiber laser using the same - Google Patents

Description

  The semiconductor laser module and the fiber laser of the present invention are used by being incorporated into a laser processing apparatus that performs thermal processing (for example, welding, cutting, etc.) of a metal material or a resin material. The present invention relates to a semiconductor laser module that is fiber-coupled efficiently and with high brightness, and a fiber laser that uses the semiconductor laser module as an excitation source.

  In recent years, laser processing apparatuses using a semiconductor laser as a light source or excitation source have been widely used for various material processing such as welding, welding, cutting, and modification.

  Among them, the fiber laser has a high-quality beam as its feature. However, with the recent progress in technology, a high-quality beam of a single mode or a low-order multimode close to it is maintained, and a very high number of kW It is possible to oscillate even a large laser output. As a result, active spread to the material processing field has been achieved.

  Advances in optical fiber technology against the background of the adoption of double-clad fibers greatly contribute to the increase in output of such fiber lasers. A typical pumping method of a fiber laser using a double clad fiber is shown in FIG.

  The double clad fiber 22 includes a core 23, an inner clad 24 that surrounds the outer periphery of the core portion, and an outer clad 25 that surrounds the inner clad 24. The signal light propagates through the core 23 in a single mode or a low-order multimode, and the excitation light includes the core 23 and propagates through the region of the inner cladding 24. Of the pumping light propagating through the inner cladding 24, the pumping light passing through the core 23 portion is excited by optically coupling the signal light propagating through the core 23 if a rare earth element is added to the core 23. Amplify.

  A method of fusion-connecting optical fiber couplers is often used for injecting excitation light into the double clad fiber 22. The optical fiber coupler 15 has a fiber bundle part 16 in which a signal optical fiber through which signal light propagates and a multimode fiber through which pumping light propagates are tightly bundled, a double clad fiber 22, and an inner clad of a double clad fiber. The fiber bundle portion 16 is melted and integrated up to a diameter of 2 mm, and is heat-stretched in a tapered shape, and is composed of a fused portion 17 optically coupled to the double clad fiber 22.

  FIG. 18 is a cross-sectional view of the fiber bundle portion 16. The fiber bundle portion 16 has a signal optical fiber 20 having a core through which signal light propagates as a center, and multimode fibers 19 through which excitation light propagates are arranged concentrically around the signal optical fiber 20 to form a fiber bundle in close contact with each other. Yes.

  The fused part cross section 21 a and the fused part cross section 21 b show the configuration of the fiber bundle section tapered in the vicinity of the fused part 17. Depending on the drawing conditions such as temperature, drawing time, and speed at the time of heat drawing in a taper shape, the shape of the cross section of the fused portion is almost similar to that of the fiber bundle portion 16 such as the cross section of the fused portion 21a. There is a variety of forms that are integrated in a circular shape by the action of surface tension as in the section 21b.

  In any case, the fiber bundle portion 16 is stretched so that its outer diameter is substantially the same as the diameter of the inner clad 24 of the double clad fiber 22, and excitation light from the plurality of multimode fibers 19 to the inner clad 24 of the double clad fiber 22. Are further fused and optically coupled to the double clad fiber 22 so that the signal light propagates correctly from the core of the signal optical fiber 20 to the core 23 of the double clad fiber 22 (or vice versa). ing.

  For example, Patent Document 1 has been proposed as a fiber laser that performs the above-described configuration and operation. Thus, it becomes possible to inject | pour big excitation light by using a double clad, As a result, it became possible to perform big amplification. At present, with the advent of fiber lasers combining such structures, a very large laser output of several KW is possible.

  A beam from the semiconductor laser is optically coupled to the multimode fiber 19 by combining a semiconductor laser serving as an excitation light source and various optical elements. That is, in order to increase the output of the fiber laser, it is important how to couple the excitation light to the multimode fiber 19 with high luminance and high density. In addition to the development of the semiconductor laser itself that outputs a higher-brightness beam to increase the brightness and density of the excitation light, the development of technology for shaping and condensing the output beam from the semiconductor laser using an optical element is also possible. It is being actively conducted.

  In addition, in order to expand the application and range of laser processing, it is necessary to reduce the apparatus cost. The ratio of the semiconductor laser to the cost of various members and materials constituting the laser processing apparatus is very large. A price per unit laser output is often used as an evaluation index of laser device cost or member cost.

  The above-described increase in the brightness of the semiconductor laser can reduce the number of semiconductor lasers to be used, and the accompanying reduction in the number of members such as optical elements, thereby reducing the device price per unit laser output.

  In addition, the use of a semiconductor laser array is often used as a means for reducing the price of a laser device. A schematic diagram of the semiconductor laser array is shown in FIG. The shape of the semiconductor laser array that is most often employed is a monolithic one-dimensional array of broad stripe semiconductor lasers, sometimes called an LD bar (semiconductor laser bar). The width of the semiconductor laser array is generally about 10 mm. The semiconductor laser array 2 has a plurality of light emitting emitters 9, and the production cost difference per semiconductor laser is small compared to a single emitter semiconductor laser, and the cost per unit laser output is kept low. Can do.

  FIG. 6 is an explanatory diagram showing how the laser light emitted from one light emitting emitter is spread. The laser light output from the light emitting emitter 9 has different divergence angles in the thickness direction (first axis) and the width direction (slow axis), and the profile is elliptical as shown in FIG. In general, first-axis laser light is close to a single mode, and its divergence angle 10 is larger than the divergence angle 11 of slow-axis, but BPP (Beam Parameter Product) is small and beam quality is good.

  For example, Patent Document 2 or Patent Document 3 has been proposed as a method of performing beam shaping and focusing using a semiconductor laser array and an optical element.

  Patent Document 2 is the simplest method for coupling a semiconductor laser array and an optical fiber. The beam irradiated from the semiconductor laser array is collimated only by the first axis by an optical lens (for example, a rod lens).

  Immediately after the optical lens, an optical element called an optical fiber array in which optical fibers are arranged on a glass substrate in accordance with the number and interval of light emitting points of the semiconductor laser array is arranged, and an irradiation beam from the semiconductor laser array is Coupled to optical fiber. The optical fiber is a multimode fiber with a core diameter of around 100 micrometers, and the optical lens is a very thin lens similar to an optical fiber. The semiconductor laser array, optical lens, and optical fiber array are several tens of micrometers. Alignment is performed in a state of close proximity.

  Not only Patent Document 2, but also a fiber coupling method having such a configuration has been conventionally used, and an irradiation beam from a semiconductor laser array can be coupled to an optical fiber with high efficiency.

  Patent Document 3 uses a mirror and a telescope arranged on a step and performs beam shaping by rotating the beam, so that the beam from multiple emitters can be condensed into one beam with high quality or fiber coupled An optical element is proposed.

  Further, if the collimation of the slow axis in addition to the first axis is used, the optical path length after the collimation can be increased, and a method such as wavelength addition or polarization addition can be used. As a result, outputs from a plurality of semiconductor lasers can be added to further increase the brightness. As described above, according to Patent Document 3, it is possible to couple the excitation light to the multimode fiber described above with high luminance and high density, and it is possible to realize high output of the fiber laser desired by the market.

Japanese Patent Application Laid-Open No. 11-072629 US Pat. No. 6,785,440 US Pat. No. 5,888,096

  Since the semiconductor laser module represented by Patent Document 2 has a simple configuration, the number of parts including optical elements is small, and the material cost can be suppressed. However, because of the configuration, the emission point of the semiconductor laser coupled to one multimode fiber is limited to one, and high brightness and high density of large excitation light cannot be expected.

  In order to construct a high-power fiber laser using this module, it is necessary to cascade the fiber lasers shown in FIG. 8 in a plurality of stages and amplify the oscillated laser beams one after another. This means that the working length of the fiber laser becomes longer depending on the degree of demand for higher output. A fiber laser with a long working length inevitably increases the number of fusion points between the fibers, which increases fusion loss and heat generation at the fusion part.

  Further, laser oscillation such as parasitic oscillation is likely to become unstable, which may cause a serious failure such as destruction of the pumping semiconductor laser due to the occurrence of an optical surge.

  On the other hand, as described above, the semiconductor laser module of Patent Document 3 can couple pumping light to a multimode fiber with high brightness and high density, so that a high-power fiber laser is configured with a short working length fiber. Can do. However, the step mirror used in this module is very expensive, and the effect of reducing the cost of the laser device by adopting the semiconductor laser array is diminished. In addition, in order to perform fiber coupling, a high level technique for properly aligning various optical elements and bonding and fixing them is required. Coupled with the relatively large number of optical elements, further technology and know-how are required to ensure long-term reliability of the semiconductor laser module.

  An object of the present invention is to provide a semiconductor laser module that is fiber-coupled at low cost and high brightness, and is particularly effective as an excitation source for increasing the output of a fiber laser.

In order to solve the above problems, a semiconductor laser module of the present invention is mounted on a first heat sink, irradiated with a laser in a first direction, and aligned with each other in a slow axis direction perpendicular to the first direction. A first semiconductor laser array having two first light emitting emitters, and at least two second light emitting emitters mounted on a second heat sink and irradiated with a laser in a first direction and aligned with each other in a slow axis direction And a second semiconductor laser array. A first fast aximate lens arranged in a direction in which the laser is emitted from the first semiconductor laser array and collimating a laser extending in a first axis direction perpendicular to the first direction and the slow axis direction; And a first slow-axis trimming lens arranged in a direction in which the laser is irradiated from the first fast-axis trimming lens and collimating the laser spreading in the slow-axis direction. Further, the second semiconductor laser array is arranged in the direction in which the laser is irradiated and collimates the laser spreading in the first axis direction, and the laser is irradiated from the second first axis laser lens. They are arranged in a direction, and a second slow axis collimating lens for collimating the laser spreading in the slow axis direction. Furthermore, a first axis condensing lens that is arranged in a direction in which the laser is irradiated from the first slow axis trimming lens and the second slow axis trimming lens and condenses the laser in the first axis direction, and a first axis condensing lens It is located in the direction of laser irradiation and focuses the laser in the slow axis direction.
And a slow axis condenser lens. Furthermore, one and the at least two second optical fibers Les chromatography The emitted from one of the radiation emitter is incident of the at least two first light emitter, and the two first light emitter of the other and two of said second optical fiber and the other laser emitted from one of the radiation emitter is incident of having an optical fiber array having at least two optical fibers. The second heat sink is located in the first axis direction at a pitch smaller than the sum of the thicknesses of the first heat sink and the first semiconductor laser array in the first axis direction with respect to the first heat sink. These heat sinks are positioned on the side opposite to the laser irradiation direction at a pitch larger than the length of the first heat sink in the first direction.

  With this configuration, the beams of the plurality of semiconductor laser arrays are optically coupled to the same number of optical fibers as the number of light emitting emitters of the semiconductor laser array.

  As described above, the present invention is low in cost by arranging a plurality of semiconductor laser arrays in a stepped manner, condensing only the first direction among the collimated beams, and optically coupling them to the optical fiber array. However, a semiconductor laser module with high brightness can be provided, and in particular, it is effective as a fiber laser excitation source.

The side view which shows the whole structure in Embodiment 1 of the semiconductor laser module of this invention The top view which shows the whole structure in Embodiment 1 of the semiconductor laser module of this invention The side view which shows the whole structure in Embodiment 2 of the semiconductor laser module of this invention The top view which shows the whole structure in Embodiment 2 of the semiconductor laser module of this invention Schematic diagram of semiconductor laser array Explanatory diagram of laser light emitted from the light emitting emitter of a semiconductor laser Schematic diagram of optical fiber array The figure which shows operation | movement description in Embodiment 3 of the fiber laser of this invention.

(Embodiment 1)
1 and 2 show an example of the configuration of the semiconductor laser module of the present invention. FIG. 1 is a side view and FIG. 2 is a plan view as viewed from above.

  The semiconductor laser module 1 is composed of the following optical components. 1 and 2, the semiconductor laser array 2 has a plurality of light emitting emitters arranged at regular intervals and oscillates laser light from each emitter. A collimating lens 3 is laser light emitted from the semiconductor laser array 2. Among them, the collimating lens 4 collimates the first axis, the collimating lens 4 collimates the slow axis among the laser beams emitted from the semiconductor laser array 2, and the condensing lens 5 collects only the first axis of the collimated laser beams. The optical fiber array 6 is a multi-mode fiber arrayed in a line on the substrate in the same number as the number of light emitting emitters of one semiconductor laser array and at the same interval as the light emitting emitter interval. An optical component to be optically coupled is shown.

  The operation of the semiconductor laser module configured as described above will be described. FIG. 5 is an enlarged view of the semiconductor laser array 2 of FIGS. As already described, the semiconductor laser array has a plurality of light emitting emitters 9 arranged side by side at regular intervals.

  In the first embodiment, as shown in FIG. 5, a case where a semiconductor laser array 2 having 6 emitters in particular is used will be described. The light emitting emitters 9 of the semiconductor laser array 2 are irradiated with laser beams having divergence angles respectively in the first axis 10 and the slow axis 11 as shown in FIG.

  The collimating lens 3 and the collimating lens 4 are aligned immediately after the semiconductor laser array 2. First, the first axis of laser light emitted from the semiconductor laser array using the collimating lens 3 is used, and then the slow axis is used using the collimating lens 4. Are collimated in sequence. In this example, since the number of light emitting emitters is six, six collimated substantially parallel beams are irradiated from the collimating lens 4.

  Subsequently, the semiconductor laser array 2, the collimating lens 3 and the collimating lens 4 are set as one set, and a plurality of sets having the same configuration are arranged in a staircase pattern. In the first embodiment, a case where there are three semiconductor laser arrays 2 will be described. Specifically, as shown in the top view of FIG. 2, the semiconductor laser arrays are arranged vertically so that the six beams from the three semiconductor laser arrays have the same optical axis when viewed from the top. As shown in the side view of FIG. 1, the three semiconductor laser arrays 2 arranged vertically are arranged in steps so as to change the height.

  The reason for arranging the semiconductor laser arrays 2 in a stepped manner is to make the intervals between the irradiation beams from the respective semiconductor laser arrays as small as possible within a range in which the irradiation beams do not interfere with the front semiconductor laser array. A semiconductor laser chip is usually mounted on a heat sink for cooling by soldering or the like, and if it is stacked vertically (stack), the beam pitch increases by the thickness of the heat sink or the like.

  As shown in FIG. 1, the pitch of the beams from each semiconductor laser array can be reduced by arranging them stepwise, and the beam quality after focusing can be greatly improved as will be described later. Thus, in this example, 18 collimated beams emitted from the three semiconductor laser arrays are arranged in an array of 6 when viewed from above and 3 from the side.

  The laser light emitted from the semiconductor laser array 2 is collimated by the collimating lens 3 and the collimating lens 4, and the beam is condensed by the condenser lens 5 only in the first axis beam.

  The three fast-axis beams shown in the side view of FIG. 1 are condensed at one point using the condenser lens 5, and the six slow-axis beams shown in the top view of FIG. At the condensing point, the number of light emitting emitters of the semiconductor laser array becomes six beams that coincide with the interval. If a multimode fiber having a light receiving angle and a core diameter suitable for the beam divergence angle and the spot diameter at the condensing point is aligned, fiber coupling can be performed.

  FIG. 7 is an enlarged view of the optical fiber array in FIGS. 1 and 2. In the optical fiber array, V-grooves are formed on the glass substrate 14 at a desired number and interval, and the optical fibers 13 are aligned and fixedly bonded thereto.

  As described above, the beam after the condenser lens 5 becomes six beams that coincide with the light emitting emitter interval of the semiconductor laser array 2 at the condensing point. If the optical fiber array 6 composed of six multimode fibers is aligned with the light emitting emitter interval of the semiconductor laser array 2 to the condensing point, the optical fibers can be optically coupled to each other.

  After the condenser lens 5, the specifications (BPP) of the multimode fiber of the optical fiber array adapted to the first axis is expressed by the following equation.

Ｆｄはマルチモードファイバのコア径、ＦΘはマルチモードファイバの受光角、Ｂｄは集光点でのビームスポット径、Ｂｅは集光点でのビーム拡がり角、Ｎはファーストアクシスのビーム数、ｆはフィルファクターと呼ばれるものでファースト方向のビーム間隔に占めるビーム幅の割合である。

Fd is the core diameter of the multimode fiber, FΘ is the receiving angle of the multimode fiber, Bd is the beam spot diameter at the condensing point, Be is the beam divergence angle at the condensing point, N is the number of beams of the first axis, and f is This is called the fill factor and is the ratio of the beam width to the beam interval in the first direction.

  The reason why the semiconductor laser arrays are arranged stepwise as described above is to make the fill factor f as large as possible, and as a result, the first-axis BPP after light collection can be made smaller.

  In the present embodiment, the case where the number of semiconductor laser arrays is three and the number of light emitting emitters is six for each semiconductor laser array has been described. However, the present invention is not limited to this range.

  The number of light emitting emitters of the semiconductor laser array directly defines the number of multimode fibers used in the optical fiber array. However, the number of semiconductor laser arrays matches the number N of first-axis beams in the above equation, and it is apparent that various values can be taken as long as the relationship in the above equation is satisfied. In other words, there are many variations other than the present example, all of which are based on the operation of the present invention.

  As described above, according to the present invention, it is possible to provide a semiconductor laser module that is fiber-coupled with high luminance at low cost without using a special optical element.

(Embodiment 2)
An example of the semiconductor laser module of the present invention that is different from the above-described embodiment will be described in detail. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  3 and 4 show an example of the configuration of the semiconductor laser module according to the present invention. A series of operations until the laser light irradiated by the semiconductor laser array 2 is condensed by the condenser lens 5 are implemented. This is the same as that described in the first embodiment.

  In the semiconductor laser module 7, a condensing lens 8 that condenses the slow axis is added to each beam condensed by the condensing lens 5. In many cases, the core diameter of the multimode fiber used in the optical fiber array 6 depends on the beam spot diameter of the slow axis. The core diameter of the multimode fiber of the optical fiber array can be reduced.

表１は実施の形態１および実施の形態２で説明した半導体レーザモジュールの実施例である。表中、モジュールＡは実施の形態１で説明した半導体レーザモジュールの一例であり、モジュールＢは実施の形態２の半導体レーザモジュールの一例である。

Table 1 shows an example of the semiconductor laser module described in the first and second embodiments. In the table, module A is an example of the semiconductor laser module described in the first embodiment, and module B is an example of the semiconductor laser module of the second embodiment.

  In both cases, the beam quality immediately before being coupled to the optical fiber array is different, and a multimode fiber having a core diameter of 400 μm is applied to the module A and a core diameter of 105 μm is applied to the optical fiber array.

  In the module A, a taper fiber that reduces the core diameter from 400 μm to the core diameter of 105 μm is fusion-spliced, and a multimode fiber having a core diameter of 105 μm is used as the output fiber of the module. This is because the power and quality of the beams output by both modules are substantially the same, and the tapered fiber used in module A has the same optical function as the condenser lens 8 of module B.

(Embodiment 3)
An example of an embodiment according to the fiber laser of the present invention will be described in detail with reference to FIG.

  By bonding the semiconductor laser module described in the first embodiment or the second embodiment to the optical fiber coupler 15 in which the multimode fiber is concentrically arranged around the signal optical fiber 20, the rare earth element is formed. The added double clad fiber 22 is excited to cause laser oscillation.

  The optical fiber coupler shown in FIG. 8 has six multimode fibers for injecting pumping light. This is the number of output fibers from the semiconductor laser module shown in the example of the first embodiment or the second embodiment. Match 6 lines. That is, the output fiber of the semiconductor laser module and the multimode fiber of the optical fiber coupler need only be fused and connected.

  The number of light emitting emitters of the semiconductor laser array may be selected according to the desired number of pumping light injection ports. According to the present invention, it is possible to inject pump light for a plurality of light emitting emitters into a multimode fiber used for pumping injection of an optical fiber coupler. Realized at low cost.

  The semiconductor laser module of the present invention can be fusion-bonded with an optical fiber combiner. An optical fiber combiner is obtained by bundling a plurality of multimode fibers and then fusing and stretching them to form a fusion connection with the multimode fiber, and is used when adding a plurality of laser powers to a single multimode fiber. If this optical fiber combiner is used, the optical output of the semiconductor laser array can be concentrated on a single multimode fiber. In addition to high-intensity excitation to the fiber laser, it can be used as a heat source for direct processing in combination with a condenser lens. Can also be used.

  The semiconductor laser module of the present invention is capable of fiber coupling a plurality of semiconductor laser arrays at low cost and high brightness. In particular, a fiber laser using this as a pumping source is thermally processed (for example, a metal material or a resin material) This is useful for a laser processing apparatus that performs welding, cutting, and the like.

1 Semiconductor laser module according to Embodiment 1 2 Semiconductor laser array 3 Collimating lens (first axis)
4 Collimating lens (slow axis)
5 Condenser lens (first axis)
6 Optical fiber array 7 Semiconductor laser module according to Embodiment 2 8 Condensing lens (slow axis)
DESCRIPTION OF SYMBOLS 9 Light emission emitter 10 First-axis spreading angle 11 Slow-axis spreading angle 12 Optical fiber array 13 Multimode fiber 14 V-groove board | substrate of an optical fiber array 15 Optical fiber coupler 16 Fiber bundle bundle 17 Fusion | fusion part 18 Sectional drawing of a fiber bundle part 19 Multimode fiber 20 Signal optical fiber 21 Cross section of fused part 22 Double clad fiber 23 Core 24 Inner clad 25 Outer clad

Claims (4)

A first semiconductor laser array mounted on a first heat sink and having at least two first light emitting emitters that are irradiated with a laser in a first direction and aligned with each other in a slow axis direction perpendicular to the first direction; ,
A second semiconductor laser array mounted on a second heat sink and having at least two second light emitting emitters irradiated with a laser in the first direction and aligned with each other in the slow axis direction;
A first fast aximate lens arranged in a direction in which laser is emitted from the first semiconductor laser array and collimating a laser extending in a first axis direction perpendicular to the first direction and the slow axis direction; ,
A first slow axis lens that is arranged in a direction in which a laser beam is emitted from the first first axis lens and collimates a laser beam that spreads in the slow axis direction;
A second fast axis lens that is arranged in a direction in which a laser is emitted from the second semiconductor laser array and collimates a laser beam that spreads in the fast axis direction;
A second slow-accelerate lens arranged in a direction in which a laser is emitted from the second first-accuracy lens and collimating a laser spreading in the slow-axis direction;
A first axis condensing lens that is arranged in a direction in which a laser is emitted from the first slow axis trimming lens and the second slow axis trimming lens and condenses the laser in the first axis direction;
A slow-axis condensing lens that is positioned in a direction in which laser is emitted from the first-axis condensing lens and condenses the laser in the slow-axis direction;
Two said first one and two of said second one optical fiber LES chromatography The irradiated is incident from one of the radiation emitter of the radiation emitter, and, two of said first light emitter An optical fiber array having at least two optical fibers of an optical fiber to which a laser beam irradiated from the other one of them and the other of the two second light emitting emitters is incident ;
The second heat sink is positioned in the first axis direction at a pitch smaller than the sum of the thicknesses of the first heat sink and the first semiconductor laser array in the first axis direction with respect to the first heat sink. And
The semiconductor laser module, wherein the second heat sink is located at a pitch larger than the length of the first heat sink in the first direction and opposite to the laser irradiation direction. The distance between the first semiconductor laser array and the first first-accurate lens is equal to the distance between the second semiconductor laser array and the second first-accurate lens;
A distance between the first fast-accurate lens and the first slow-accurate lens is equal to a distance between the second first-accurate lens and the second slow-accurate lens;
The distance between the first semiconductor laser array and the first axis condenser lens is smaller than the distance between the second semiconductor laser array and the first axis condenser lens,
The at least four lasers emitted from at least two of the first light emitting emitters and at least two of the second light emitting emitters reach the fast axis condenser lens substantially parallel to each other in a fast axis direction and a slow axis direction. Item 2. The semiconductor laser module according to Item 1 . 3. The semiconductor laser module according to claim 1, wherein the number and interval of the first light emitting emitters, the number and interval of the second light emitting emitters, and the number and interval of the optical fibers are equal. An optical fiber coupler in which a signal optical fiber through which signal light propagates and a multimode fiber through which pumping light propagates are tightly bundled;
A semiconductor laser module according to any one of claims 1 to 3 ,
A fiber laser in which the optical fiber coupler and the optical fiber array are fusion-connected.

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